Résumé : Equipoise is defined by Freedman (1987, p.141) as a "state of genuine uncertainty on the part of the clinical investigator regarding the comparative therapeutic merits of each arm in a trial." This principle is grounded in the ethical motivation that any ex-ante preference for a given option would undermine the interests of those who are offered another. Randomized controlled trials (RCTs) in development economics disregard the equipoise requirement by typically disadvantaging the control group. This paper investigates how the equipoise principle is formalized in the medical literature and discusses whether and how it should be taken into consideration by economists. It argues that equipoise is especially relevant when double (or even single) blindness is excluded and when the control group includes already vulnerable individuals. More generally, this paper advocates for developing a vibrant ethics conversation on the design and fairness of RCTs in social sciences.